The subject invention is directed to a single solution bonding formulation, a method for treating dentin or enamel with the same, and a method for making the single solution bonding formulation. More particularly, the subject invention is directed to a single solution bonding formulation which provides a physical barrier to bacteria, toxins and other caries producing agents while permitting fluoroapatite and/or hydroxyapatite to form under and/or around the physical barrier.
Teeth are structured with an outer enamel layer, a middle dentin layer, and an inner pulp layer. The pulp contains the living tissue of the tooth, including vasculature and nerve endings. The dentin layer, which surrounds the pulp, contains mostly hydroxyapatite and collagen. Hydroxyapatite forms when calcium hydroxides react with phosphate in the proper amounts and under the right conditions. Hydroxyapatite has the formula Ca5(PO4)3OH. Dentin may also contain fluorapatite. Fluorapatite forms when fluoride precipitates with calcium and phosphate in the proper amounts and under the right conditions. Fluorapatite has the formula Ca5(PO4)3F. The enamel, which covers the dentin, is a very hard protective layer.
Bacteria present within the oral cavity convert sugar and starch into acid by-products. The acid by-products can dissolve the enamel layer of a tooth and create a hole in the enamel layer, called a cavity. The acid-by-products can then continue to react and dissolve the underlying dentin. Hydroxyapatite (e.g., in dentin) is particularly sensitive to acid dissolution. Ultimately, if left untreated, the pulp will be exposed to bacteria including their acid by-products and may eventually die as a result. Once substantial damage to the pulp has occurred, one may require a root canal to remove dead tissue. Also, other corrective steps (e.g., placement of post, cap, and crown) may be required to prevent further decay. It would be desirable to prevent tooth decay before reaching the point of requiring extensive root-canal work.
Thus, it would be more desirable to repair or reconstruct the damaged dentin or enamel before the pulp is infected or otherwise injured. Not only is it desirable to repair and/or reconstruct the damaged dentin or enamel, but it is also desirable to provide a physical barrier over the same dental structures to prevent further deterioration.
Treatment of damaged dental structures (e.g., dentin, enamel, etc.) typically consists of applying a bonding agent to a cavity to permanently adhere a restorative filling material, e.g. composite resin, to the tooth structure to provide a physical barrier against further damage by bacteria and their acid by-products. Exemplary bonding formulations are disclosed in U.S. Pat. Nos. 4,918,136; 5,767,170; 6,114,408; 6,206,959; and 6,210,759. Typical bonding agents used to treat a damaged tooth do not, however, promote repair of the underlying dental structures in situ.
Thus, there is great need for a formulation that has adhesive properties and acts as a physical barrier and yet promotes the in situ restoration and/or repair of the underlying dental structures (e.g., enamel and/or dentin) by inducing the precipitation of minerals such as hydroxyapatite and/or fluorapatite. It is desirable to provide the above-noted formulation in a single-solution (ie., avoid two-or-more multipart-formulations) type formulation for convenience, and ease of use.
It is an object of this invention to provide a single solution bonding formulation for dental applications for bonding to dentin and/or enamel to provide a physical barrier against further deterioration while providing release of calcium, phosphate and/or fluoride sufficient to deposit fluorapatite and/or hydroxyapatite at the site of tissue, dentin or enamel damage.
It is another object of this invention to provide a method for preparing a single solution bonding formulation for bonding to dentin and/or enamel while providing release of calcium, phosphate and/or fluoride sufficient to incorporate fluorapatite and/or hydroxyapatite to strengthen, impart greater resistance to decay, and repair or restore missing or decayed dental structures.
It is still another object of this invention to provide a method for treating dentin, enamel, or pulp with the above noted single solution bonding formulation(s).
These and other objects of the invention are provided by one or more embodiments described below. In one embodiment, a single solution bonding formulation for dental applications is provided. The formulation comprises:
(a) a plurality of a self-polymerizable polyvinyl acidic monomer or a plurality of at least two different polymerizable polyvinyl acidic monomers,
(b) a calcium phosphate filler,
(c) at least one polymerization photoinitiator,
(d) optionally, an accelerator,
(e) optionally, a solvent, and
(f) optionally, a fluoride additive.
The monomers noted as (a) above should be provided in an amount sufficient to form a physical barrier over the dental structure, and mediate bonding between the tooth structure and an overlying restorative material, preferably with a shear bond strength of at least about 28 MPa.
According to another embodiment of the invention, a method for preparing the above-noted single solution bonding formulation is provided. The method comprises the step of:
mixing together:
(a) a plurality of a self-polymerizable polyvinyl acidic monomer or a plurality of at least two different polymerizable polyvinyl acidic monomers,
(b) a calcium phosphate filler,
(c) at least one polymerization photoinitiator,
(d) optionally, an accelerator,
(e) optionally, a solvent, and
(f) optionally, a fluoride additive.
According to still another embodiment of the invention, a method for treating enamel, dentin, or pulp, is provided. The method comprises the steps of:
(a) applying to the enamel, dentin, or exposed pulp the above-noted single solution bonding formulation; and
(b) then exposing the applied single solution bonding formulation to light sufficient to polymerize the single solution bonding formulation.
According to another embodiment of the invention, another method to treat enamel, dentin, or pulp is provided. Such a method further comprises conditioning the enamel, dentin, or pulp before applying the above noted single solution polymerization formulation as noted in step (a).